如何在页面上绘图？

不知道asp.net中的报表能不能帮助你解决，它一般的可以解决柄图，柱桩图，曲线图等等，并且可以根据数据时时的更新图

你只要把绘图过程放置在ONPAINT事件中，不就实现了吗？

<%@ Page Language="vb" Debug="True" %>
<%@ import namespace="system.drawing" %>
<%@ import namespace="system.drawing.imaging" %>
<%@ import namespace="system.drawing.drawing2d" %>
<%
dim strFilename as string
dim i as System.Drawing.Image
strFilename = server.mappath("./chris-fsck.jpg")

i = System.Drawing.Image.FromFile(strFilename)

dim b as New system.drawing.bitmap(i.width, i.height, pixelformat.format24bpprgb)
dim g as graphics = graphics.fromimage(b)

g.clear(color.blue)

'旋转图片
i.RotateFlip(System.Drawing.RotateFlipType.Rotate90FlipX)
g.drawimage(i,New point(0,0))
i.RotateFlip(System.Drawing.RotateFlipType.Rotate270FlipY)

g.RotateTransform(10)
g.drawimage(i,New point(0,0))
g.RotateTransform(10)
g.drawimage(i,New point(20,20))
g.RotateTransform(10)
g.drawimage(i,New point(40,40))
g.RotateTransform(10)
g.drawimage(i,New point(40,40))
g.RotateTransform(-40)
g.RotateTransform(90)
g.drawimage(i,New rectangle(100,-400,100,50),New rectangle(20,20,i.width-20,i.height-20),GraphicsUnit.Pixel)
g.RotateTransform(-90)

' 拉伸图片
g.drawimage(i,New rectangle(10,10,50,50),New rectangle(20,20,i.width-20,i.height-20),GraphicsUnit.Pixel)
g.drawimage(i,New rectangle(50,10,90,50),New rectangle(20,20,i.width-20,i.height-20),GraphicsUnit.Pixel)
g.drawimage(i,New rectangle(110,10,150,50),New rectangle(20,20,i.width-20,i.height-20),GraphicsUnit.Pixel)


'切割图片
g.drawimage(i,50,100,New rectangle(180,80,60,110),GraphicsUnit.Pixel)
g.drawimage(i,140,100,New rectangle(180,80,60,110),GraphicsUnit.Pixel)

'旋转图片
i.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipX)
g.drawimage(i,230,100,New rectangle(180,110,60,110),GraphicsUnit.Pixel)

response.contenttype="image/jpeg"

b.save(response.outputstream, imageformat.jpeg)

b.dispose()

%>

嗬嗬，给我分吧！http://www.ourasp.net/content.asp?kind=ASPPLUS&title=ASP.NET画图全攻略（上）/&keyword=aspplus应用下，自己找吧！核心的机制是这样的：由此，我们完成了利用asp.net技术画图的过程。
综合起来，可以总结出以下几点：1.利用ASP.NET技术，可以在不使用第三方组件的情况下，画出理想的图形。2.画图核心是构造一个BitMap（位图）对象，它为要创建的图形提供了内存空间。然后，利用有关namespace提供的类和方法画出图形。最后就可以调用Bitmap对象的“Save”方法，将其发送到任何.NET的输出流中，这里是直接将图形的内容发送到浏览器，而没有将其保存到磁盘中。这不是我写的，作者是：bben_h。主要是save之后到一个输出流，基本原理就是这个。

ok，这次你可以名正言顺的给我分了，我做了一个小试验，你把你得page_load的代码替换成下面这样。关键的依据就是bm.Save。private void Page_Load(object sender, System.EventArgs e){
System.Drawing.Bitmap bm = new System.Drawing.Bitmap(800,100);
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bm);
g.Clear(System.Drawing.Color.Blue);
g.DrawString("中华人民共和国",new Font("Tahoma",72),Brushes.Black,new PointF(5,5));
bm.Save(Response.OutputStream,ImageFormat.Gif);
bm.Dispose();
g.Dispose();
}嗬嗬，给我分吧！你作有向图干什么？

概念纠偏：楼上一个兄弟说OnPaint事件，我认为这是不对的。web应用下，这个事件已经没有意义（因为有了客户端）上面代码核心的地方，就是把你要画的图，事先做成一个object，然后以静态的形式，放到page上。就像mbm兄写的那样。所有的核心，就在bm.Save方法上。仔细想一想，你就明白了！

哦,虽然不能帮你,但是帮你UP一下!希望你能得到好的解答!
UP! :)

juqiang(方枪枪)说的没有错，我的OnPaint事件只有在WINDOWS 应用中才有效，在WEB中根本就不存在这样的事件。我始终以为不能在WEB下绘图的，因为浏览器不支持，就好象我想定义一个DROPDOWNLIST一样，使其LISTITEM是一个CALENDAR是不可能的。不过，如果通过SERVER端绘制图形后保存到一个静态的图形文件然后再在浏览器中使用例外。谢谢你提供资料，我去看看。

ai_daoluan鸟人，赶快结帐！不要耽误时间，如果没时间，我替你写这个程序！如果转载bben_h兄的文章，请大家注意不要把它的名字忘记加上。

显示叶面：
<%@ Page Language="vb" %>
<%@ Import Namespace="System.Data"%>
<%@ Import Namespace="System.Data.Sqlclient"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>Display_Chart</title>
<meta name="GENERATOR" content="Microsoft Visual Studio .NET 7.0">
<meta name="CODE_LANGUAGE" content="Visual Basic 7.0">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
</head>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">
<table width="100%" height="100%">
<tr>
<td align="middle">
<IMG Src="http://wujiahong/Bjbys/manage_platform/stu_job/I_Charts.aspx?table=<%=request.querystring("table")%>">
</td>
</tr>
</table>
</form>
</body>
</html>
画图叶面：
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.Data
Imports System.Data.SqlClient
Public Class Charts
    Inherits System.Web.UI.Page
    Dim Values As ArrayList = New ArrayList()
    Dim Captions As ArrayList = New ArrayList()
    Dim Connection As SqlConnection
    Dim DR As SqlDataReader
    Dim Command As SqlCommand
    Dim TableName As String
    Dim SumNum As Int32
    Dim Item_Count As Integer
#Region " Web Form Designer Generated Code "    'This call is required by the Web Form Designer.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()    End Sub    Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
        'CODEGEN: This method call is required by the Web Form Designer
        'Do not modify it using the code editor.
        InitializeComponent()
    End Sub#End Region
    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        TableName = Request.QueryString("table")
        Connection = New SqlConnection(Application("SqlConString"))
        '统计数据到两个数组
        ReadData()
        '生成饼图
        DisplayPieChart()
    End Sub
    'This function returns a color for the bar and pie charts.
    Private Function GetColor(ByVal itemIndex As Integer) As Color
        Dim objColor As Color
        Select Case itemIndex
            Case 0
                objColor = Color.Blue
            Case 1
                objColor = Color.Red
            Case 2
                objColor = Color.Yellow
            Case 3
                objColor = Color.Purple
            Case 4
                objColor = Color.Orange
            Case 5
                objColor = Color.Brown
            Case 6
                objColor = Color.Gray
            Case 7
                objColor = Color.Maroon
            Case Else
                objColor = Color.Green
        End Select
        Return objColor
    End Function
    Sub ReadData()
        Dim SqlString As String
        Dim I As Integer
        Dim Num_Temp As Int16
        SumNum = 0
        I = 0
        SqlString = "Select r1,count(r1) as cc from " + TableName + " group by r1"
        Command = New SqlCommand(SqlString, Connection)
        Command.Connection.Open()
        DR = Command.ExecuteReader
        While DR.Read
            Captions.Add(Convert.ToString(DR.GetString(0)))
            Values.Add(Convert.ToInt16(DR("cc")))
            Item_Count += 1
            SumNum = SumNum + Convert.ToInt16(DR("cc"))
        End While
        DR.Close()
        Command.Connection.Close()
    End Sub
    Sub DisplayPieChart()
        '定义显示的字体
        Dim FontLeg As Font
        Dim FontTitle As Font
        FontLeg = New Font("宋体", 10)
        FontTitle = New Font("宋体", 15)        '确定图片的大小，及其各个元素的大小,宽度都一样
        Dim ImageWidth As Integer
        Dim ImageHeight As Integer        Dim ChartHeight As Integer
        Dim LegendHeight As Integer
        Dim TitleHeight As Integer        Dim BufferSpace As Integer = 15
        ImageWidth = 300        LegendHeight = FontLeg.Height * (Item_Count + 1) + BufferSpace
        TitleHeight = FontTitle.Height + BufferSpace
        ChartHeight = ImageWidth
        ImageHeight = ImageWidth + LegendHeight + TitleHeight + BufferSpace        '画出底图
        Dim WjhBitmap As Bitmap
        Dim WjhGraphic As Graphics
        Dim WjhBrush As Brush
        WjhBitmap = New Bitmap(ImageWidth, ImageHeight)
        WjhGraphic = Graphics.FromImage(WjhBitmap)
        WjhBrush = New SolidBrush(Color.Black)
        WjhGraphic.FillRectangle(New SolidBrush(Color.White), 0, 0, ImageWidth, ImageHeight)        ' 画出饼图
        Dim PieRec As Rectangle
        PieRec = New Rectangle(0, TitleHeight, ImageWidth, ChartHeight)
        Dim CurrentDegree As Single = 0.0F
        Dim I As Integer
        For I = 0 To Item_Count - 1
            WjhGraphic.FillPie(New SolidBrush(GetColor(I)), PieRec, CurrentDegree, Convert.ToSingle(Values(I) / SumNum * 360))
            CurrentDegree = CurrentDegree + Convert.ToSingle(Values(I) / SumNum * 360)
        Next        '画出标题
        Dim TitleRecF As RectangleF
        TitleRecF = New RectangleF(0, 0, ImageWidth, TitleHeight)
        Dim WjhFormat As StringFormat = New StringFormat()
        WjhFormat.Alignment = StringAlignment.Center
        WjhFormat.LineAlignment = StringAlignment.Center
        WjhGraphic.DrawString("统计结果", FontTitle, WjhBrush, TitleRecF, WjhFormat)        '画出图例
        WjhGraphic.DrawRectangle(New Pen(Color.Black, 2), 0, ImageHeight - LegendHeight, ImageWidth, LegendHeight)
        For I = 0 To Item_Count - 1
            WjhGraphic.FillRectangle(New SolidBrush(GetColor(I)), 5, ImageHeight - LegendHeight + FontLeg.Height * I + 5, 10, 10)
            WjhGraphic.DrawString(Captions(I) + " ---- " + Convert.ToString(Values(I)), FontLeg, WjhBrush, 20, ImageHeight - LegendHeight + FontLeg.Height * I + 1)
        Next        '画总计
        WjhGraphic.DrawString("总计: " + Str(SumNum), FontLeg, WjhBrush, 5, ImageHeight - FontLeg.Height - 5)
        WjhBitmap.Save(Response.OutputStream, ImageFormat.Jpeg)
    End Sub
End Class

现在的画图程序，怎么都是用vb写的呀？？我好像从来没看到过用C#写的代码~

结账了，aidaoluan!!!要不扣你的奖金啊！！！

调试易

如何在页面上绘图？

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